KABUL -- Afghan detainees held at the U.S. military prison at Guantanamo Bay, Cuba, are being transferred home to face closed-door trials in which they are often denied access to defense attorneys and the U.S. evidence being used against them, according to Afghan officials, lawyers and international rights groups.

Since October 2006, the United States has transferred approximately 50 detainees out of Guantanamo to the custody of the Afghan government, part of a policy aimed at reducing the prison population and ultimately closing the facility. Once home, many of the Afghans have been left in a legal limbo not unlike the one they confronted while in U.S. custody.

"These people have been thrown into a deeply flawed process that convicts people on inadequate evidence and breaks numerous procedural rules of Afghan law and human rights standards," said Jonathan Horowitz, an investigator at One World Research, a public interest investigation firm that works with attorneys and advocacy groups on human rights cases and has monitored some of the detainees' trials.

At least 32 detainees transferred from Guantanamo are being held in a high-security wing of Afghanistan's Pul-i-Charki prison, near Kabul. Built with U.S. funds and opened in April 2007, the wing is known as Block D or Block 4. Many detainees in that wing have been held for months without being charged or tried, according to interviews with detainees' relatives, American and Afghan lawyers familiar with their cases and one detainee who has been released.

Frustration with the process has been mounting among the detainees and their advocates. Early this year, about 20 detainees at Block D sent a petition to officials in Kabul asking them to look into why their cases had stalled. When the petition appeared to go unanswered, several detainees sewed their mouths shut with wire and thread and went on a hunger strike, according to Hayatullah al-Hashimi, a former deputy justice minister who visited the prison at the time.

The protest prompted Afghan President Hamid Karzai to send a government delegation to Block D to investigate. Hashimi said the detainees abandoned their hunger strike after officials vowed to review their cases. "They were very determined. They said, 'We just want to get our cases moving so they won't be sitting there static,' " Hashimi said. "Their general problem was that they wanted to know what their destination was, and they should know that. It is their right."

Zalmay Rasul, Afghanistan's national security adviser and lead overseer of the country's detainees, said that the legal process at Block D is "not perfect" but that many of the problems stem from Afghanistan's struggle to rebuild its frayed judicial infrastructure during a conflict that has severely strained resources. After 30 years of successive conflicts, and authoritarian rule under the Taliban, the country has essentially had to build its legal institutions from scratch, he said.

"After the attacks of 9/11 and the beginning of the war on terrorism, Afghanistan was a destroyed state," Rasul said. "Nobody knew who was who. There is no identification card. There is no file on these people. Today, we are just rebuilding our judicial system."

'No Guarantee of Anything'

For several years after the 2001 U.S.-led invasion of Afghanistan, detainees held at Guantanamo were set free once they returned to this country, due largely to its weak government and lack of infrastructure. But in 2005, American officials began negotiating an agreement that called for the U.S. government to provide Afghanistan with $20 million in aid to build Block D, train detention officials to run it, and develop a set of legal mechanisms. Since the invasion, the United States has pledged at least $160 million for judicial reform in Afghanistan, according to the State Department.

Sandra L. Hodgkinson, deputy assistant secretary of defense for detainee affairs, said it was the Afghan government's decision to try detainees in its courts for crimes allegedly committed on its soil, rather than holding them indefinitely as "enemy combatants," as the United States initially had suggested. Since then, the United States has been closely tracking the criminal cases, but American officials said they do not have any control over the trials or the Afghan justice system.

Those tried in the Afghan system have included former Guantanamo detainees, as well as some of the more than 220 detainees transferred to Block D from the U.S. military prison at Bagram air base.

"There is no guarantee of anything other than the government is going to use their own justice system for crimes the detainees may have committed," Hodgkinson said.